Method of producing steel strapping



United States Patent 3,311,512 METHOD OF PRODUCING STEEL STRAPPINGAugust F. Mohri and John F. Jarrell, Hamilton, Ontario, and Robert C.Reynolds, Burlington, Ontario, Canada, assignors to The Steel Company ofCanada, Limited, Hamilton, Ontario, Canada, a Canadian company NoDrawing. Filed Apr. 2, 1964, Ser. No. 356,950 Claims priority,application Canada, Mar. 17, 1964, 898,040 6 Clm'ms. (Cl. 148-121) Thisinvention relates to 'a method of producing high tensile steel strappingand the product produced thereby. It is particularly directed to theproduction of high tensile steel strapping from a silicon semi-killedsteel or a capped steel having from about 0.24% to about 0.30% carbonand from about 1.35% to about 1.65% manganese.

Heretofore, high tensile steel strapping commonly has been produced bytreating carbon steels having a carbon content of from about 0.45% toabout 0.55% and a manganese content of from about 0.60% to about 0.90%by cold reducing the steel to the desired gauge, slitting thecold-reduced steel longitudinally into a plurality of strips of thedesired width, feeding the cold-reduced strips continuously into afurnace for heating the strips to a temperature above the critical rangeand passing the strips into a lead bath held at a predeterminedtemperature to promote the development of the final desired grainstructure and physical charcteristics as 'a result of isotherm-a1transformation.

A disadvantage inherent in this method of producing steel strapping isthe requirement for expansive heat treating equipment such as furnacesdesigned especially to heat treat the cold-rolled steel.

It is, therefore, 'an important object of the present invention toprovide a method of producing high-strength steel strapping whichobviates the need for expensive heat treating equipment and permits theproduction of high strength steel strapping using stress relievingequipment readily available in conventional steel mills.

It is another important object of the present invention to produce steelstrapping having the desired properties of strength and ductility from asemi-killed or capped steel.

Another important object of the present invention is the provision of asimple and inexpensive method for the production of steel strapping.

These and other objects of the present invention, and the manner inwhich they can be attained, will become apparent from the followingdetailed description of the method of the invention.

We have found that the strength 'and ductility requirements of a highstrength steel strapping can be obtained by means of the presentinvention from a semi-killed steel having from about 0.01% to about0.05% silicon or a capped steel having a minor residual silicon content,each having a carbon content of from about 0.24% to about 0.30% and amanganese content of from about 1.35% to about 1.65%, the optimumresults being obtained when the carbon content is 0.27% and themanganese content is 1.50%.

Hot rolled steel strip in the form of coils having this metallurgicalcomposition are cold worked by rolling or the like means 'and reducedabout 60% to about 70% in thickness to provide a steel strip having athickness of from 18 to 23 gauge United States Standard or the likedesired gauge thickness. The cold-reduced steel is then stress relievedby process annealing at a temperature of from about 850 F. to about 950F., preferably at about 900 F., in 'a controlled neutral or slightlyreducing atmosphere for about 6 hours. The steel is then cooled in theneutral or slightly reducing atmosphere to about ICC atmospherictemperature and slit longitudinally to provide the narrow strappingstrips of a desired width such as A3", 1% and 2" widths from theoriginal full Width coil strip. If it is preferred to provide apredetermined degree of surface texture or smoothness to the strappingthe strip can be temper rolled or skin passed prior to the slittingstep.

The stress relieving of the steel 'at this temperature results inpartial recrystallization or grain alteration of the crystallinestructure of the deformed steel to provide the required steel ductilityand other physical characteristics while retaining the desired tensilestrength. For example, steel strapping according to the presentinvention 1%" in width and about 20 gauge in thickness has a breakingload of 5200 pounds and an elongation of from about 8% to about 10% insix inches.

The present invention provides a number of important advantages. Highstrength standard and heavy-duty steel strapping having the desiredductility and other physical properties necessary for utilization inbanding or otherwise strapping cartons, boxes and the like objects canbe produced from a steel of a specific metallurgical composition withoutthe need for the expensive heattreating equipment heretofore necessary.The steel strapping thus can be readily and inexpensively produced inconventional steel mills employing standard low-temperature processannealing equipment.

It will be understood, of course, that modifications can be made in thepreferred embodiment of the invention described and illustrated hereinwithout departing from the scope and purview of the invention as definedby the appended claims.

What we claim as new and desire to protect by Letters Patent of theUnited States is:

1. The method of producing high tensile steel which comprises the stepsof cold working a steel having from about 0.24% to about 0.30% carbon'and from about 1.35% to about 1.65% manganese to reduce the thicknessabout 60% to about 70% such that the said steel attains the desiredgauge thickness, annealing said steel at a temperature between about 850F. to about 950 F. for about 6 hours to obtain the desired grainstructure and ductility, and cooling the steel to atmospherictemperature.

2. The method of producing high tensile steel strapping which comprisesthe steps of cold working a strip of steel having from about 0.24% toabout 0.30% carbon and from about 1.35 to about 1.65% manganese toreduce the thickness of the strip about 60% to about 70% such that thesaid strip attains the desired gauge thickness, heating the cold-reducedstrip to and maintaining said strip at a temperature between about 850F. to about 950 F. for about 6 hours to obtain the desired grainstructure and ductility, and cooling the strip to atmospherictemperature.

3. The method of producing high tensile steel which comprises the stepsof cold rolling a steel strip having a carbon content of about 0.27% anda manganese content of about 1.50% about 60% to about 70% in thicknesssuch that the said steel strip attains the desired gauge thickness,annealing the cold rolled steel strip at a temperature of about 900 F.for about 6 hours to obtain the desired grain structure and ductility,and cooling the strip in a protective atmosphere to atmospherictemperatures.

4. The method of producing high tensile steel strapping which comprisesthe steps of cold working a steel strip having a carbon content of about0.27% and a manganese content of about 1.50% to reduce the strip about60% to about 70% in thickness such that the said steel strip attains thedesired gauge thickness, anneala 4% ing the cold worked steel strip at atemperature of References Cited by the Examiner about 900 F. for about 6hours to obtain the desired UNITED STATES PATENTS grain structure andductility, cooling the strip in a protective atmosphere to a temperaturebelow about 200 F., 2364507 12/1958 Rfinkm and slitting that strip intorelatively narrow strips of a 5 OTHER REFERENCES deslred Wldth' MetalsHandbook, 1948, Am. Soc. for Metals, pages 5. The method as claimed inclaim 2 in which the 354455 cooled strip is slit into relatively narrowstrips of desired Width DA ID L RECK P E 6. A high tensile steelstrapping produced according to 10 V mary mmmel' the method claimed inclaim 2 H. F. SAlTO, Asszstant Exammer.

4. THE METHOD OF PRODUCING HIGH TENSILE STEEL STRAPPING WHICH COMPRISESTHE STEPS OF COLD WORKING A STEEL STRIP HAVING A CARBON CONTENT OF ABOUT0.27% AND A MAGANESE CONTENT OF ABOUT 1.50% TO REDUCE THE STRIP ABOUT60% TO ABOUT 70% IN THICKNESS SUCH THAT THE SAID STEEL STRIP ATTAINS THEDESIRED GAUGE THICKNESS, ANNEALING THE COLD WORKED STEEL STRIP AT ATEMPERATURE OF ABOUT 900*F. FOR ABOUT 6 HOURS TO OBTAIN THE DESIREDGRAIN STRUCTURE AND DUCTILITY, COOLING THE STRIP IN A PROTECTIVEATMOSPHERE TO A TEMPERATURE BELOW ABOUT 200*F., AND SLITTING THAT STIPINTO RELATIVELY NARROW STRIPS OF A DESIRED WIDTH.